Electron discharge device



March 5, 1 946. o. H. FULTON, JR I 2,396,179

ELECTRON DISCHARGE DEVICE Fild Jan. 18, 1945 2 Sheets-Sheet 1 j 53 H UFI m 132 v J! I I? :1 35 4 1 I '17 i '1 f 18 i 1 a f March 5; 1946. Y OFULTON, JR 2,396,170

ELECTRON DISCHARGE DEVICE Filed Jan. 18, 1945 z'sheets-sheet 2 [5% "1 IINVENTOR.

OLIVER H, FULTON JR associated. circuits, particularly where PatentedMar. 5, 1946 Oliver Fultom'Jh, Montclaii'; 3., assignor to Radio-Corporation of America, a corporation of Delaware Application January1-8, 1945, Serial No.-57.3,343

'9 Claims.

My invention relates to electron discharge devices and particularlytosuch devices useful-at. very high frequencies.

When an electron discharge device: is to be used as an amplifier or as amixer at ultrahigh. frequencies, a lownoise. level is a primary con.-sideration. Best results require the useiof a high vacuum triode.Howevenin triodes used as: radiov frequency amplifiers, feedbackbeco'mesa prob.- lem. To eliminate the need for neutralization due toundesired regeneration, when the device is used as a radio frequencyamplifier, it is coerated as a grounded grid triode and the input andoutput must be well shielded from each other to bring about low feedbackcapacity, that is plate-to-cathode and heater.

Since lead inductance and interelectrode'capacity are limiting factorsin high frequency op eration, these must be kept at-a minimum. At highfrequency, transit time loading is a problem which must. be overcome byclosespaci ng of ele* ments introducing. a manufacturing problem inassembly. High transconductance and amouerately high amplificationfactor'a're also desirable features. Lightweight construction with allelectrode leads coming through one end of the envelope simplifies andreduces the size of the lumped p'arameters are used.

It is, therefore, an object of my invention to provide an improvedelectron discharge device useful as an amplifier or mixer at ultra highfrequencies of the order of 500 megacycles. V

Another object of my inventionis to provide such a device having a lownoise level, that is a high signal-to-noise ratio.

A particular object of my invention is to pro vide an electron dischargedevice of the triode type, suitable for use as a grounded grid amplifieror mixer and particularly adaptable for use with circuits having lumpedparameters; 7

A further object of my invention is to provide such a device having ahigh transconductance and moderately high amplification factors,

Another object of my invention'i'stoprovide a device of this kindhaving. low inductance high radio frequency conductance. v

A further object of my invention is to provide such a device inwhichsmallinterelectrode ca- 50 pacityl with resultant low inputandoutputcapacitiesand low feedback capacity are provided.

V A still further object of my invention is to provide, such adevice inwhich: the transit time load-- ing factors are small; f

(01. zoo-#275) These and other objects will appear hereinafter. Thenovel features which I believeto be characteristic of my inventionare-set forthwith particularity in the appended claims, but theinvention itself will best be understood by reference-to the followingdescription taken in connection with the accompanying drawings in whichFigure l is a side elevation of an electron discharge device madeaccording to; my'inventio'n; Figurerz is a view of Figurel turned 90,Eigure 3 is a section taken along the line 3".3 ofFigure 1, Figure 4 isasection taken along the line' l l of Figure 1, Figurefi is a-sectiohtaken along the line'5-.5:of Figure 1,. Figure 6 shows a typical.groundedgrid circuit utilizing a tube made according to my in.- vention,and Figures 7 to 9,. inclusive, are enlarged viewsofa. detail of theconstruction used in an electron discharge device made according to myinvention.

Referring to the drawings, an electron discharge device made accordingto my invention includes an evacuated envelope I0 having a'fiat press H.and. the usual plurality oflead l2 sealed therethrough and arranged inav circle, the press the usual emitting coatingare a pair of anodemembers l1 and [8 having a U-shaped transverse section, the closed endsof the ui'being fiat andoppositely disposed to the emitting surfaces ofthe cathode. These anode elements arecut back as at I1 and I8 to'reducethe cathode-- anode capacity While at the same time providingthe'necessarysurface registering with the emitting surfaces of thecathode to receive-all'the electrons "therefrom. These anode elementsare strapped together bymeans of strapping elements 19 and 20. Thismount assembly-is received between and supported by a pair of spacedinsu-' lating spacer members 2| and '22, preferably of mica. They areprovided with the proper apertures for receiving the ends ofthe-cathode, grid side rods andthe anode or plate ears, such asI'8"'a'nd' IT.

According to my invention the device is pri .-marily to operate with agrounded grid circuit In accordance with. invention I provide cathodeand thecath'ode heat which extend through appropriate apertures in themica spacer 2| and are folded over to securely lock the mica shield andgrid together. The

shield is provided with a pair of arcuate shaped flaps or aprons 30 and3! which, as shown in Figures 1 to 3 inclusive, are formed to providethe necessary shielding. Flap 3| is folded over the trough to completelyshield the upper end of the cathode from the ears of the anode and theflap is bent over the upper ears of the plate member I1. Thus no part ofthe cathode directly sees the anode outside the grid-cathode space andcomplete shielding results.

Mounted at the lower end of the mount assem bly is a second shieldmember 25 substantially like that at the top of the mount assembly. Thisbottom shield member, however, is provided with a strap 36 at the lowerend of which is mounted a transverse shielding disc 31 which extendsclose to the top of the press I l and is received between the variousleads arranged in a circle.

. The bottom shield 25 is electrically connected to the lower ends ofthe grid side rods 15 and IE.

However, in this case the tabs corresponding to 26 and 21 are removedfrom the shield. In their place U-shaped elements 4| and 49 are used,the end view of which is shown in Figure l, the side view in Figure 2and in section in Figure 3. These U-shaped elements have a pair ofoppositely disposed dependent legs such as 40' and 4! which may bewrapped around and welded to the lead wires. nected to a pair ofoppositely disposed leads in the press, the leads lying in the sameplaneso that the press is bisected by the shield and leads.

The downwardly extending legs are con In assembly the elements 40 and Alare first The cathode is provided with a strap 42 connected to. anotherlead I2 oppositely disposed to the anode lead, and the two heater leadsl3 are connected to two other leads [2. These connectors and leads areshielded from the strap 39 and its associated lead by the apron or skirt35, and the lower ears on the anode element l8 are shielded from thecathode and cathode heater leads by the skirt 25 which is formed toextend transversely of the mount and parallel to the'base and extendsbetween the lower ears of anode element l8 and the cathode strap andheate leads.

Thus it is apparent that the anode and cathode are completely shieldedfrom each other at all points, including the connectors and leads, andthat this arrangement permits an external shield to be connected to theoppositely disposed contact leads and pins connected to the bottomshield so that externally the input and ouput circuits may also beshielded from each other, thus preventing regeneration.

A getter ring 32 may be secured to this top shield by means of the strap33. All of the connectors between the contact pins and leads and thevarious electrodes are wide straps which have low loss and lowconductance. Because of the high turns-per-inch of the grid wires, inthe example shown 240 turns per inch of 1.2 mil wire was used, and theclose spacing between plate and grid of the order of 15 mils, hightransconductance and low transit time loading results. A

transconductance of between 11,000 and 12,009

. micromhos with an amplification factor of 55 has been obtainedwithdevices made according to my invention, the whole arrangement beingplaced in an envelope less than two inches in length and three quartersof an inch in diameter.

While I have indicated the preferred embodiments of my invention ofwhich I am now aware and have also indicated only one specificapplication for which my invention may be employed, it will be apparentthat my invention is by no means limited to the exact forms illustratedor the use indicated, but that many variations may be made in theparticular structure used and the purpose for which it is employedwithout departing from the scope of my invention as set forth in theappended claims.

What I claim as new is: v

1. An electron discharge device having an envelope including cathode,grid and anode electrodes, said cathode electrode and said anodeelectrode having leads, said grid electrode having a shield providedwith a skirt adjacent the anode electrode leadand positioned between theanode lead and the cathode lead, said envelope having a, press, apluralityof leads extending through said press, said'grid shield beingcon nected to leads oppositely disposed across said press whereby thespace between the press and said electrodes is dividedinto two shieldedcompartments.

2. An electron discharge device having an envelope provided with a pressat one end thereof, a plurality of leads extending through said press, amount within said envelope comprising a cathode, grid and anodesupported on said leads, said grid being provided with shields forshielding said anode from said cathode, said cathode and said anodebeing connected to leads oppositelydisposed across said press, said gridshield being connected to leads atopposite sides of said press, saidlast leads lying in a-plane passing between said cathode lead and saidanode lead. 1

3. An electron discharge device having an envelope provided with a pressatone end thereof, a plurality of leads arranged in a circle extendingthrough said press, a mount Within'said envelope comprising acathodagrid and anode supported on said leads, said grid having a shieldfor shielding said anode from said cathode, said cathode and said anodebeing connected to leads disposed on opposite sides of said circle, saidgrid shield being provided with connectors connected to leads onopposite sides of said circle, said last leads lying in a planepassingbetween said cathode lead and said anode lead. r

4. An electron dischargedevice including an envelope having a pressprovided with a plurality of leads extending therethrough, a mountsupported within said envelopeand including a cathode,- a gridsurrounding said cathode, and an anode outside of said gr'idQa connectorconnected between the anode and a lead in'said press, and a.

connector connected between said cathode and a lead in said pressoppositely disposed to said lead connected to said anode, said gridbeing provided with a shield connected thereto and positioned betweenthe press and said grid, said shield being provided with a skirtadjacent said anode lead for shielding said anode lead from said cathodelead, said shield being connected to other leads in said press, saidother leads lying in a plane passing between the anode lead and thecathode lead.

tween said spacing members, and an anode outside of said grid andpositioned between said spacing members, said cathode, grid and anodeextending through said spacer members, a low inductance lead connectedbetween the anode and a lead in said press, and a low' inductance leadconnected between said cathode anda lead in said press oppositelydisposed to said lead connected to said anode, said grid being providedwith a shield connected thereto and positioned between the press and oneof said insulating spacer members, said shield being provided with askirt adjacent said anode lead for shielding said anodev lead from saidcathode lead, said shield being provided with a pair of oppositelydisposed low inductance connectors connected to other leads lying in aplane passing between the anode lead and the cathode lead.

6. An electron discharge device including an envelope having a press, aplurality of leads extending through said press and arranged around saidpress, a mount supported by said leads and including a fiat cathode, aflat grid surrounding said cathode and provided with a pair of side rodslying in a plane parallel to the fiat side of said grid, and anodeelements positioned adjacent the flat sides of said cathode and grid, ashield connected to the side rods of said grid adjacent said press, ananode lead extending from one of said anode elements and connected to alead in said press, a cathode lead extending from said cathode andconnected to a lead in said press oppositely disposed to the anode lead,said shield having an apron adjacent said anode lead, a shield lyingparallel to the press and within the space defined by the leads in saidpress and connected to said apron, a second apron on said shieldextending parallel to the press and positioned between the anode andsaid cathode lead.

7. An electron discharge device including an envelope having a press, apluralityof leads extending through said press and arranged in a circle,a mount supported by said leads and including a cathode, a gridsurrounding said oathode and provided with a pair of side rods lying ina plane, and an anode adjacent the grid, a shield connected to the endof the side rods of said grid adjacent said press, said anode beingconnected to a lead in said press, said cathode being connected to alead in said press opp sitely disposed to the anode lead, said shieldhaving an apron adjacent said anode lead, a shield lying parallel to thepressand within the circle defined by the leads in said press andconnected to said apron, a second apron on said shield extendingparallel to the press andpositioned between the anode and said cathodelead, and connections between the shield and oppositely disposed 1eadslying inthe plane of said side rods.

8. An electron discharge device including an envelope having a press, aplurality of leads extending through said press and arranged around saidpress, a mount supportedby said leads and including a flat cathode, aflat grid surrounding said cathode and provided with a pair of side rodslying in a plane parallel to theflat sides of said cathode, and anodeelements positioned adjacent the flat sides of said cathode and grid, ashield connected to the grid side rods at each end of said grid, ananode element being connected to a lead in said press, said cathodebeing connected to a lead in said press oppositely disposed to the anodelead, the shield adjacent thepress being provided with an apron adjacentsaid anode lead, a shield lying parallel to the press and within thespace defined by the leads in said press and connected to said shield, asecond apron on said last mentioned shield extending paralle1 to thepress and positioned between an anode and said cathode lead, the shieldat the end of said grid remote from said press having an apron foldedover the ends of the grid side rods and the end of said cathode remotefrom said press.

9. An electron discharge device including an envelope having a press, aplurality of'leads extending through said press and arranged in a aflattened grid surrounding said cathode and provided with a pair of siderods lying in a plane parallel to the fiat sides of said cathode, andanode elements positioned adjacent the flat sides of said cathode andgrid and having ears extending through said mica spacers, a shieldconnected to the side rods at each end of said grid on the outside ofthe space between said spacers, said anode elements being connected to alead in said press, said cathode being connected to a lead in said pressoppositely disposed to the anode lead, the grid shield adjacent thepress having an apron adjacent said anode lead, a shield lying parallelto and adjacent the press and'within the circle defined by the leads insaid press and connectedtosaid apron, a second apron on said lastmentioned grid shield extending parallel to tho press and positionedbetween an anode ear and a said cathode lead, the shield at the end ofsaid grid remote from said press having a skirt extending over an anodeear, and a second skirt folded over the ends of the grid side rods andthe end of said cathode remote from said press.

OLIVER H. FULTON, JR.

